The present invention relates to a superconducting apparatus and a method of operation, or more in particular to a superconducting apparatus comprising an emergency gas discharge pipe for discharging the gas generated in a cryostat at the time of quenching as an emergency measure.
In the case where a superconducting apparatus such as a superconducting magnet apparatus is operated, the superconducting magnet itself may be burnt by the electromagnetic energy stored in the superconducting magnet at the time of transition to normal conductive state, i.e., during quenching.
Generally, in order to avoid this burning, energy consumption means, i.e., a protective resistor (or a protective diode) is connected in parallel to the superconducting magnet, so that the energy stored in the superconducting magnet is consumed as heat in the resistor, and at the same time the gas generated in the cryostat is discharged out of the cryostat as an emergency measure through an emergency gas discharge pipe mounted on the cryostat.
FIG. 11 shows the general configuration of a superconducting magnet apparatus in common use. This superconducting magnet apparatus has therein a cryostat 1 which hermetically contains a very low temperature refrigerant, i.e., liquid helium 7 and also a superconducting magnet 2 installed therein.
The superconducting magnet 2 is connected to a power supply 4 through a power lead 3. A breaker 5 and a protective resistor 6 are interposed between the power supply 4 and the superconducting magnet 2. The superconducting magnet 2 in the cryostat 1 is cooled by the refrigerant liquid helium 7 to assure satisfactory heat exchange thereof.
A radiation shield plate 10 is mounted in the space between the surface of the liquid helium in the cryostat and the flange 9 above the cryostat in order to prevent penetration of heat by radiation and convection from the upper flange 9 side. Also, the upper flange 9 has mounted thereon a recovery port 11 for recovering the evaporated helium gas under steady-state operation and an emergency gas discharge pipe for releasing a great amount of evaporated helium gas at the time of quenching the superconducting magnet 2.
The component part designated by reference numeral 13 mounted midway of the emergency gas discharge pipe 12 is an emergency valve (safety valve) constructed in such a manner as to open in case of emergency (at the time of quenching). Although the drawing under consideration shows that a vent 14 of the emergency gas discharge pipe is adapted to open in the vicinity of the cryostat, the vent 14 is normally mounted in such a manner as to discharge the gas outdoor ten and several meters to several tens of meters away.
In a superconducting magnet apparatus constructed in the above-mentioned way, assume the operation of a magnet apparatus having a central generated magnetic field of 6 T, an outer dimension of 1.5 m and a height of about 1 m. The crystat has an inner diameter of about 2 m and a height of about 4 m, and has liquid helium of about 5 cubic meters stored therein.
Helium of course evaporates under steady-state operating conditions. The amount of helium evaporated under steady-state operating conditions, however, is not very great and, for the superconducting magnet apparatus of the above-mentioned capacity, is considered about 100 liter per hour in terms of liquid helium. The amount of evaporation is about 80 kiloliters per hour in terms of gas. This much quantity can be recovered sufficiently by the emergency gas discharge pipe 12 of about 10 cm in diameter.